Ventilation module for an aero-refrigeration tower including a free wheel for drawing in outside air and for outputting air

ABSTRACT

A ventilation unit for an air-cooling tower and comprising a freewheel for drawing outside air and for discharging air in the upper portion of the ventilation unit. The freewheel has a rear face and a front face, the freewheel draws the outside air according to the direction of the axis of rotation of the freewheel by the front face and discharges the air radially to the axis of rotation of the freewheel, the ventilation unit being passed through by a drawing passage of outside air and by a discharge passage of air, the discharge passage of air directing the flow of air to the front of the plane formed by the front face. The subject matter also relates to an air-cooling tower and a method for drawing and for discharging air in such a ventilation unit.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a ventilation unit intended for an air-cooling tower, the ventilation unit comprises in particular a freewheel for drawing outside air and for discharging air in the upper portion of the ventilation unit. This invention also relates to an air-cooling tower provided with such a ventilation unit associated with a mixed unit and a dry unit for the passage of the air.

PRIOR ART

According to prior art, it is known to use a freewheel in association with a ventilation unit for the drawing of outside air and the discharging of air to the upper units which are the wet unit then the dry unit.

Such prior art is known in document US2005/0056042.

The term freewheel refers to a fan-motor assembly fixed onto a plate. This fan-motor assembly can be housed in a casing which is most often rectangular.

The freewheel draws the air from a side referred to as the upstream side, pressurises the air and discharges it onto a side referred to as the downstream side to the units. Therefore according to prior art space must be provided on two opposite sides of the freewheel for respectively one or several drawing passages of outside air and one or several discharge passages.

In addition, such a freewheel is frequently arranged outside of the ventilation unit by being arranged in a casing, which increases its encumbrance.

Such an outside positioning of the freewheel subjects it to inclement weather and does not provide hardly any attenuation of its noise during operation, with this noise being limited only by the presence of the casing of the freewheel.

An object of this invention is therefore to propose a ventilation unit with a drawing and a discharging of air that is more effective and less cumbersome with, where applicable, a freewheel that is more effectively protected for external stresses than in prior art.

Another object of this invention is to propose a ventilation unit and an air-cooling tower with optimised internal air circulation, and an orientation of the internal air flows.

SUMMARY OF THE INVENTION

For this purpose, this invention relates to a ventilation unit intended for an air-cooling tower, the ventilation unit comprising a freewheel for drawing outside air and for discharging air in the upper portion of the ventilation unit, characterised in that the freewheel has two faces, a so-called rear face and a so-called front face, said freewheel draws the outside air according to the direction of the axis of rotation of said freewheel and discharges radially to the axis of rotation of said freewheel, with the ventilation unit being passed through by at least one drawing passage of outside air and by at least one air discharge passage, said at least one air discharge passage being configured to direct the flow of air to the front of the plane formed by the front face, opposite the rear face.

Indeed the outside air passes through in a first step the drawing passage wherein the air is at a first pressure. Downstream of the freewheel, on the contrary, the flow of air is at a second pressure that is higher than the first. The air is therefore conveyed under pressure to the rest of the installation.

Such a freewheel in a ventilation unit according to this invention allows for a drawing and a discharging on the same side of the freewheel, which allows for a supply and a removal of the air extending substantially in parallel and saves space in the ventilation unit. The freewheel puts the drawn air under pressure which is then removed to a mixed unit of the air-cooling tower by the discharge passage or passages. While in prior art, the wet device is a unitary set, the invention combats this bias and procures a mixed operation to a stage, referred to as mixed unit, of which only a portion is dedicated to the wet function device.

The discharging and the drawing are carried out in different directions and there is no interference with the discharging and the drawing flows, with the freewheel drawing the outside air according to the direction of the axis of rotation of said freewheel and discharging the air in the same axis, and optionally as a by-pass radially to the axis of rotation of said freewheel.

The invention also relates to an air-cooling tower comprising a mixed unit and a dry unit, with the dry unit being superimposed on the mixed unit, characterised in that it comprises such a ventilation unit, with the mixed unit being superimposed on the ventilation unit.

In particular in the particular case for which there is a passage as a by-pass associated with the freewheel, such a tower allows for better guiding of the air of the ventilation unit to the mixed unit, with the mixed unit able to comprise two separate enclosures of which one for the humidification of the air and the other allowing for the passage of a flow of discharged air while still retaining it as is.

The invention also relates to a method for drawing and for discharging air in a ventilation unit of such an air-cooling tower, wherein the drawing and the discharging of the air are carried out on the same side of the freewheel being separated from one another, with the pressure of the outside air being increased during the drawing by a lateral air inlet in the drawing passage. The pressurising is carried out in a drawing passage through the lateral intake of additional air in addition to the air penetrating through a mouth of the drawing passage, with this additional air passing under a discharge passage.

BRIEF DESCRIPTION OF THE FIGURES

The purposes and objects, as well as the characteristics and advantages of the invention shall appear better in the detailed description of an embodiment of the latter which is shown by the following accompanying drawings wherein:

FIG. 1 diagrammatically shows a perspective view of an embodiment of an air-cooling tower according to this invention with in particular a ventilation unit,

FIG. 2 diagrammatically shows a top view in perspective of an embodiment of a ventilation unit that is part of an air-cooling tower according to this invention,

FIG. 3 diagrammatically shows a perspective view of an embodiment of an air-cooling tower according to this invention, with the air-cooling tower operating according to a dry mode,

FIG. 4 diagrammatically shows a top view in perspective of an embodiment of a ventilation unit that is part of an air-cooling tower according to this invention, with the air-cooling tower operating in dry mode,

FIG. 5 diagrammatically shows a perspective view of an embodiment of an air-cooling tower according to this invention, with the air-cooling tower operating according to a wet mode,

FIG. 6 diagrammatically shows a top view in perspective of an embodiment of a ventilation unit that is part of an air-cooling tower according to this invention, the air-cooling tower operating in a wet mode,

FIGS. 7 and 8 diagrammatically show a perspective view from two different viewing angles of an embodiment of a ventilation unit according to this invention provided with two compartments for freewheel.

The drawings are provided by way of example and do not limit the invention. They constitute diagrammatical block diagrams intended to facilitate the comprehension of the invention and are not necessarily at the scale of the practical applications. In particular the dimensions of the various parts do not represent reality.

In what follows, reference is made to all of the figures taken as a combination. When reference is made to one or several specific figures, the other figures are to be taken in combination with these specific figures for the recognition of the designated numerical references that are not shown on these specific figures.

DETAILED DESCRIPTION OF THE INVENTION

Before beginning a detailed review of the embodiments of the invention, optional characteristics are announced hereinafter that can possibly be used in association or alternatively:

-   -   the ventilation unit comprises at least one discharge passage         configured to direct the air in a direction perpendicular to the         direction of the axis of rotation of said freewheel.     -   the ventilation unit integrates the freewheel inside of it.         Contrary to most ventilation units known in prior art for which         a fan is outside of the unit, in this invention, the freewheel         is integrated inside the ventilation unit. The freewheel is as         such better protected from inclement weather while the noise         from its operation will be attenuated by the at least one         drawing passage, reducing undesirable noise. The ventilation         unit is also more compact by having less encumbrance.     -   the ventilation unit is passed through by at least one drawing         passage of outside air and by at least two symmetrical air         discharge passages on either side of the drawing passage         according to a plane, with this plane being preferably vertical         and advantageously containing the axis of rotation of the         freewheel, said at least one drawing and discharging passage         extend substantially parallel to one another by being         partitioned in relation to one another. Finally, the outside air         passes through a partitioned passage, with advantageously a         configuration placing the outside air in a vacuum. The air in a         slight vacuum will pass through the freewheel and be discharged         upwards without the discharge air and the drawn air being in         contact. The partitioning of the drawing and discharging         passages also makes it possible to better direct the flows of         air to the freewheel for the flow of drawn air and in the same         axis or optionally as a by-pass to the top of the ventilation         unit and a mixed unit intended to be superimposed on the         ventilation unit for the flow of discharged air.     -   said at least one drawing passage communicates with the         freewheel, on the front face of said freewheel.     -   the circulation of air is done with a speed component according         to the axis of rotation of the freewheel in the opposite         direction in a discharge passage with respect to the circulation         of air in an air drawing passage.     -   at least three discharge passages are provided, with two         discharge passages inserting an air drawing passage between         them.     -   said at least one discharge passage has a bottom with at least a         portion of the bottom in the form of s slope having a non-zero         inclination, in particular from 3% to 30%, and/or preferably         less than or equal to 5%, with preferably two vertical surfaces         on either side of said slope (18), said at least one discharge         passage opening into the upper portion of the ventilation unit.         The slope makes it possible to drain the water to the basin and         to direct the discharge air to the top of the ventilation unit,         therefore in the direction of a mixed unit superimposed on the         ventilation unit.     -   advantageously, the dimension of the drawing passage, according         to the direction of the axis of rotation of the freewheel, is         between 30% and 85%, and more preferably between 60% and 70%,         more particularly 66%, of the total dimension of the unit         according to this direction.     -   said at least one drawing passage has at least one lateral grid         arranged under the slope of said at least one discharge passage.         This grid allows for the lateral introduction of outside air         that has not penetrated through the mouth of the or of each         drawing passage but is located under the discharge passage. This         grid has the advantage of constituting an additional air intake,         increasing the air intake surface and decreasing the front speed         of the air at the drawing of the ventilation unit.     -   said at least one drawing passage has a bottom that extends         substantially horizontally when the ventilation unit is in         vertical position and said at least one drawing passage has two         substantially vertical lateral partitions, a roof closing the         drawing passage on the upper face of the drawing passage. Each         drawing passage is as such partitioned. The vertical position of         the ventilation unit corresponds to one or several drawing         passages that extend substantially horizontally in the         ventilation unit.     -   the roof is sloped by having two faces inclined towards a         respective lateral partition. The declivity of the roof allows         the water falling from the mixed unit intended to be found in an         embodiment above the ventilation device to drain to the bottom         of the ventilation unit.     -   the unit is a rectangle parallelepiped having a length and a         width, said at least one drawing and discharging passage         extending in the width of the ventilation unit, said at least         one freewheel being positioned towards a longitudinal edge of         the unit.     -   said at least one freewheel is housed in a compartment, said at         least one drawing passage opening into the compartment and said         at least one discharge passage leaving the compartment.     -   the compartment has a pierced ceiling and is provided with at         least one element for closing off for at least one passage as a         by-pass of said at least one discharge passage.     -   said at least one element for closing off the compartment is         mobile in position for opening or closing the passage as a         by-pass. This makes it possible to adjust the by-pass flow         intended for the mixed unit with this by-pass flow not passing         advantageously by at least one humidification device integrated         into the mixed unit.     -   said at least one element for closing off can be adjusted in         intermediate positions to a complete opening or closing.     -   the unit has an inclined water collector basin arranged under         the freewheel, with the basin being inclined in order to drain         the water to the outside of the ventilation unit.     -   the air-cooling tower can comprise a mixed unit (3) comprising         an air humidification device and a passage as a by-pass and a         dry unit, with the dry unit being superimposed on the mixed         unit, with the tower further comprising a ventilation unit         according to any of claims, with the mixed unit (3) being         superimposed to the ventilation unit.     -   for the air-cooling tower, the mixed unit comprises a first         enclosure that has at least one device for humidifying the air         passing through it and a second enclosure as a by-pass         connecting the ventilation unit to the dry unit with a         circulation of air without humidification from the ventilation         unit to the dry unit, with the second enclosure located above a         compartment that houses the freewheel with a ceiling pierced         with at least one element for closing off.     -   for the method, the drawing and the discharging of the air are         of the same side of the freewheel by being separated from one         another.     -   for the method, the air discharged by the ventilation unit         passes through the mixed unit by passing through the air         humidification device and the passage as a by-pass without         humidification treatment in order to penetrate into the dry         unit.

The front of the plane formed by the front face of said freewheel means the space between the opening of the drawing passages and the plane formed by the front face of said freewheel.

By referring in particular to FIG. 1, this invention relates to a ventilation unit 4 intended for an air-cooling tower 1. Such an air-cooling tower 1 comprises a ventilation unit 4, a mixed unit 3 and a dry unit 2. The mixed unit 3 is superimposed on the ventilation unit 4 and the dry unit 2 is superimposed on the mixed unit 3 by forming a vertical tower. This is valid for a vertical air-cooling tower 1 but the units 2 to 4 can also be adjacent to one another, with the air-cooling tower 1 then extending horizontally.

As can be seen in particular in FIGS. 1, 3 and 5, the dry unit 2 can comprise a dry battery 14. This dry battery 14 can be a battery with vanes that substantially takes the dimensions of at least one humidification device integrated into the mixed unit 3.

In FIGS. 3 and 5, several arrows can be seen with respect to the air flows. In these figures, the arrow F1 symbolises the flow of outside air drawn in the ventilation unit 4. The arrow F2 symbolises the flow of air discharged by the freewheel 10 rotating according to the arrow Fr. The arrow F3 indicates the flow of air that has left the ventilation unit 4 via said at least one discharge passage referenced as 12 in FIG. 2 and passing through said at least one humidification device 5 of the mixed unit 3.

The arrow F4 indicates the flow of air in the passage as a by-pass 6 of the air having left the ventilation unit and not passing through said at least one humidification device 5. The arrow F5 indicates the flow of air passing from the mixed unit 3 to the dry unit 2, with this air able to be the flow of air passing through said at least one humidification device 5.

The arrow F6 indicates the first flow of air having been conducted by the passage as a by-pass 6 of said at least one humidification device and passant in the dry unit 2 and the arrow F7 indicates the second flow of air having been conducted by the passage as a by-pass 6 of said at least one humidification device and passing in the dry unit 2, with the latter introduced between the mixed unit 3 and the dry unit 2 so that the air as a by-pass is distributed over the largest surface possible of the dry battery of the dry unit 2, with this arrow F7 being shown only in FIG. 3 for a dry operating mode of the air-cooling tower 1.

Said at least one humidification device integrated into the mixed unit 3 can successively comprise successively superimposed on the dry unit 2 a sprayed battery 15, a spraying device 16 and a drop separator 17.

For a tower 1 extending vertically, the ventilation unit 4 can comprise a freewheel 10 for drawing outside air and for discharging air in the upper portion of the ventilation unit 4, upper portion which is adjacent to the mixed unit 3.

According to this invention, the freewheel 10 draws the outside air according to the direction of the axis of rotation of said freewheel 10 and discharges the air radially to the axis of rotation of said freewheel 10. The ventilation unit 4 is passed through by at least one air discharge passage 12, said at least one air discharge passage 12 being configured to direct the flow of air according to at least one direction other than the direction of the axis of rotation of said freewheel 10.

This can be seen in particular in FIG. 2. Said at least one drawing passage 11, in FIG. 2 two drawing passages, opens onto a freewheel 10. There is advantageously one freewheel 10 for each drawing passage 11.

In the non-limiting embodiment of FIG. 2, at least two air drawing passages 11 can be provided. In this case, at least one discharge passage 12 can be inserted between the two air drawing passages 11, with the circulation of air taking place in the opposite direction in a discharge passage 12 with respect to the circulation of the air in an air drawing passage 11. Generally, it is preferable to have two symmetrical discharge passages 12 surrounding a drawing passage 11.

Still in the non-limiting embodiment of FIG. 2, at least three discharge passages 12 can be provided, with two discharge passages 12 inserting an air drawing passage 11 between them.

The discharging passage or passages 12 are to be directed to the mixed unit 3 which is located above the ventilation unit 4. For this the discharge passage or passages 12 can have a bottom with at least a portion of the bottom in the form of a slope 18 directed towards the top of the unit 4 in order to direct the discharge air towards an upper portion of the ventilation unit 4. The substantially horizontal portion of the bottom is close to the freewheel 10, with the slope 18 succeeding to this portion and terminating it towards an upper face of the ventilation unit 4 intended to be adjacent to the mixed unit 3.

The ventilation unit 4 can be passed through by at least one drawing passage 11 of outside air and by at least one air discharge passage 12. Said at least one drawing and discharging passage 11 then extends substantially in parallel to one another by being partitioned with respect to one another.

The presence of the slope 18 clears a portion of the lateral side of the or of each drawing passage 11. It is possible to provide this portion of the lateral side of the drawing passage 11 with at least one grid 19 arranged under the slope 18 of the associated discharge passage 12.

Indeed, as can be seen in particular in FIG. 4, outside air, symbolised by the arrow F1 a showing a lateral drawn flow penetrates under the slope 18 and could not join the freewheel 10 as it is enclosed under the slope 18. The presence of at least one grid 19 allows for the reintroducing of this air in an adjacent drawing passage 11.

With regards to the or each drawing passage 11, this passage has a bottom that extends substantially horizontally when the ventilation unit 4 is in vertical position, which is frequently its optimum working position.

As is notably and in particular visible in FIG. 2, the or each drawing passage 11 can have two substantially vertical lateral partitions 20. A roof 21 can close the drawing passage 11 on the upper face of the drawing passage 11. This roof 21 is advantageously sloped by having two faces inclined towards a respective lateral partition 20. This allows for the flow of the water that can fall from the mixed unit 3.

The ventilation unit 4, as moreover the other units of the air-cooling tower 1, can be a rectangle parallelepiped that has a length and a width. In this case, the drawing and discharging passages extend in the width of the ventilation unit 4. The freewheel or freewheels 10 each correspond to a pair of drawing 11 and discharging 12 passages and are positioned towards a longitudinal edge of the unit. The drawing 11 and discharging 12 passages therefore laterally pass through the ventilation unit 4, and this by rising for the discharge passage or passages 12.

As can be seen in particular in FIGS. 2, 4, 6 to 8, the freewheel or freewheels can be housed in a specific compartment 22 for each freewheel 10. Two compartments 22 are particularly visible in FIGS. 7 and 8. In these FIGS. 7 and 8, the elements for closing off have been removed and the openings 13 a that the elements for closing off can open or close can be seen. The vertical faces forming the rear face of the ventilation unit 4, of which one is removed in FIG. 7 in order to see the rear face of the freewheel 10, can advantageously be mobile. Indeed the latter can either be removed or slide relation to the others in order to facilitate access to the freewheel 10 in the event of handling.

By referring to all of the figures, the drawing passage or passages the open into the compartment 22 of their associated freewheel 10 and the discharge passage or passages 12 exit the compartment 22 of their associated freewheel 10. The compartment 22 of each wheel can have a pierced ceiling and be provided with at least one opening 13 a which can close an element for closing off 13 for at least one passage as a by-pass 6 of said at least one discharge passage 12.

This element for closing off 13 can be a flap or a set of blades of a flap or also a pull bar. The element or elements for closing off 13 the compartment 22 can be adjustable in position in order to open or close the passage as a by-pass 6. This passage as a by-pass 6 is intended to open into the mixed unit 3 without passing through said at least one humidification device 5 present in the mixed unit 3 in order to bring dry air without humidification to the dry unit 2.

The element or elements for closing off 13 can be adjustable in intermediate positions with complete opening or closing. As such, the flow rate of the flow of air passing as a by-pass of said at least one humidification device 5 can be adjusted. The adjusting can be accomplished by a servo-motor.

The ventilation unit 4 can have an inclined water collector basin 23 arranged under the freewheel 10. This basin 23 can be located under a compartment 22 surrounding the freewheel 10. The basin 23 can be inclined in order to evacuate the water to the outside of the ventilation unit 4, this underneath a wall of the compartment 22.

As mentioned hereinabove, the invention also relates to an air-cooling tower 1 comprising a mixed unit 3 and a dry unit 2, with the dry unit 2 being superimposed on the mixed unit 3. The tower comprises a ventilation unit 4 such as described hereinabove, with the mixed unit 3 being superimposed on the ventilation unit 4.

The discharge passage or passages 12 of air terminate in a portion of the mixed unit 3 integrating said at least one humidification device whether active or inactive and the passage or passages for the by-pass penetrate into the mixed unit 3 without passing through said at least one humidification device 5 this opening directly into the dry unit 2.

The mixed unit 3 can as such comprise a first enclosure 7 that has said at least one air humidification device 5 passing though it and a second enclosure 8 with an air circulation without humidification from the ventilation unit 4 to the dry unit 2. The second enclosure 8 can be found above the compartment 22 housing the freewheel 10 with a pierced ceiling of at least one element for closing off 13 when such a compartment 22 is present in the ventilation unit 4. The first and second enclosures 7, 8 are separated by an airtight wall 9.

The invention also relates to a method for drawing and for discharging air in a ventilation unit 4 of such an air-cooling tower 1, wherein the drawing and the discharging of air is carried out on the same side of the freewheel 10 be being separated from one another.

In general such a freewheel 10 comprises a front surface and a rear surface separated by a tranche. The front surface is used for drawing and the rear surface is used for discharging. In the framework of the invention, it is the same front or rear surface that is used for both drawing and discharging.

Advantageously, the front or rear surface that is not used for drawing or for discharging is backed against the inside of a wall of the ventilation unit 4, which procures a savings in terms of space. For example, when the freewheel 10 defines a cylinder, the drawing and the discharging are carried out on the same circular face of the cylinder, therefore in the same half-space with respect to the plane of this face.

The surface of the intake of the outside air in the drawing passage 11 can be increased during the drawing via a lateral air intake 19. This is carried out by introducing outside air via the lateral grid 19 that is carried by the drawing passage 11 under a slope 18 with an adjacent discharge passage 12.

In the method for drawing and for discharging air, air discharged by the ventilation unit 4 can pass through the mixed unit 3 without humidification treatment in order to penetrate into the dry unit 2.

The invention is not limited to the embodiments described hereinabove and extends to all of the embodiments covered by the claims.

REFERENCES

-   1. Air-cooling tower -   2. Dry unit -   3. Mixed unit -   4. Ventilation unit -   5. Humidification device -   5 a. Passage of humidification -   6. Passage as a by-pass -   7. First enclosure -   8. Second enclosure -   9. Wall -   10. freewheel -   11. Drawing passage -   12. Discharging passage -   13. Element for closing off -   13 a. Opening -   14. Dry battery -   15. Sprayed battery -   16. Spraying device -   17. Drop separator -   18. Slope -   19. Grid -   20. Lateral partition -   21. Roof -   22. Compartment -   23. Basin -   F1. Flow of drawn air -   F1 a. Lateral flow of drawn air -   F2. Flow of discharged air -   F3. Flow of air of said at least one humidification device -   F4. Flow of air as a by-pass of said at least one humidification     device -   F5. Flow of air between mixed unit and dry unit -   F6. First flow of air from the passage as a by-pass -   F7. Second flow of air of the passage as a by-pass -   Fr. Direction of rotation of the freewheel 

1. Air-cooling tower comprising a mixed unit comprising an air humidification device and a passage as a by-pass and a dry unit, with the dry unit being superimposed on the mixed unit, with the tower further comprising a ventilation unit, with the mixed unit being superimposed on the ventilation unit, and wherein said ventilation unit comprise a freewheel for drawing outside air and for discharging air in the upper portion of the ventilation unit, the freewheel has two faces, a rear face and a front face, said freewheel draws the outside air according to the direction of the axis of rotation of said freewheel by the front face and discharges the air radially to the axis of rotation of said freewheel, the ventilation unit being passed through by at least one drawing passage of outside air and by at least one air discharge passage, said at least one air discharge passage being configured to direct the flow of air to the front of the plane formed by the front face, opposite the rear face.
 2. Air-cooling tower according to claim 1 wherein at least one discharge passage is configured to orient the air in a direction perpendicular to the direction of the axis of rotation of said freewheel.
 3. Air-cooling tower according to claim 1, wherein the ventilation unit integrates the freewheel inside thereof.
 4. Air-cooling tower according to claim 2, wherein the ventilation unit is passed through by at least one drawing passage of outside air and by at least two symmetrical air discharge passages on either side of the drawing passage, said drawing and discharging passages extend substantially parallel to one another by being partitioned with respect to one another.
 5. Air-cooling tower according to claim 4, wherein said at least one drawing passage communicates with the freewheel, on the front face of said freewheel.
 6. Air-cooling tower claim 4, wherein the circulation of air is carried out with a speed component according to the axis of rotation of the freewheel in the opposite direction in the discharge passage in relation to the circulation of air in the air drawing passage.
 7. Air-cooling tower according to claim 6, wherein at least three discharge passages are provided, with two discharge passages inserting an air drawing passage between them.
 8. Air-cooling tower according to claim 1, wherein the dimension of the drawing passage, according to the direction of the axis of rotation of the freewheel, is between 30% and 85%, and more preferably between 60% and 70%, more particularly 66%, of the total dimension of the unit according to this direction.
 9. Air-cooling tower according to claim 8, wherein said at least one drawing passage has at least one lateral grid arranged under the slope of said at least one discharge passage.
 10. Air-cooling tower according to claim 1, wherein said at least one drawing passage has a bottom that extends substantially horizontally when the ventilation unit is in vertical position and said at least one drawing passage has two substantially vertical lateral partitions, a roof enclosing the drawing passage on the upper face of the drawing passage.
 11. Air-cooling tower according to claim 10, wherein the roof is sloped by presenting two inclined faces towards a respective lateral partition.
 12. Air-cooling tower according to claim 1, which is a rectangle parallelepiped having a length and a width, said at least one drawing and discharging passage extending in the width of the ventilation unit, said freewheel being positioned towards a longitudinal edge of the unit.
 13. Air-cooling tower according to claim 12, wherein said freewheel is housed in a compartment, said at least one drawing passage opening into the compartment and said at least one discharge passage exiting the compartment.
 14. Air-cooling tower according to claim 13, wherein the compartment has a pierced ceiling and is provided with at least one element for closing off for at least one passage as a by-pass of said at least one discharge passage.
 15. Air-cooling tower according to claim 14, wherein said at least one element for closing off the compartment is mobile in position in order to open or close the passage as a by-pass.
 16. Air-cooling tower according to claim 15, wherein said at least one element for closing off is adjustable in intermediate positions to a complete opening or closing.
 17. Air-cooling tower according to claim 1, which has an inclined water collector basin arranged under the freewheel, with the basin being inclined in order to drain the water outside of the ventilation unit.
 18. Air-cooling tower according to claim 1, wherein the mixed unit comprises a first enclosure that has at least one device for humidifying the air passing though it and a second enclosure as a by-pass connecting the ventilation unit to the dry unit with a circulation of air without humidification, with the second enclosure being located over a compartment housing the freewheel with a ceiling pierced with at least one element for closing off.
 19. Method for drawing and discharging air in a ventilation unit of an air-cooling tower according to claim 17, wherein the drawing and the discharging of air are carried out on the same side of the freewheel by being separated from one another.
 20. Method according to claim 19, wherein the air discharged by the ventilation unit passes through the mixed unit by passing through the air humidification device and/or the passage as a by-pass without humidification treatment in order to penetrate into the dry unit. 